 Sangeeth SG |
sensor size is 1/2.5 why most of the point and shoot cameras sensor size is 1/2.5"
|
|
|
|
||
|
Alan N. Marcus |
Hi Sangeeth, Electronic photography has its roots in the 1950’s technology of the TV camera. Early TV cameras were enormous. The camera lens projects an image of the outside world on the surface of a vacuum tube made by RCA called an Orthicon. Soon the Orthicon was replaced by a more efficient and smaller Vidicon tube. These tubes were glass cylinders. They were available in a variety of sizes which were designated by the diameter of the cylinder. When viewed from the front you could see a glass circle that constrained a rectangular imaging area. These tubes were replaced by a CCD (charged coupled device) silicon based imaging chip. The label used to name these chips as to size is a relic. They are named based on the vacuum tube diameter they replaced. CCD chips are made to various sizes. They start as a thin circular disk of silicon (a type of ceramic glass like material. The diameter of the blank disk is the measurement you are asking about. A CCD 1/2.5 is made from a disk that starts out as a 2 ½ inches in diameter disk. The finished chip has an imaging surface measuring about 4.3mm x 5.8mm. By comparison, 35mm film has an imaging size of 24mm x 36mm. Size matters as the larger the chip the more light sensitive picture elements (pixels) it can hold. A higher count yields better picture quality. Additionally bigger chips permit larger pixels. The larger the pixel the greater its capture area meaning its sensitivity to light is greater. This is important as reduced sensitivity generally translates to more noise. Noise is generated when a site is wrongly tripped by stray energies. Noise degrades an image. As the electronics of cameras evolves expect the light sensitive chips to get smaller and smaller with more and more pixels. Alan Marcus (dispenses marginal technical counsel)
|
|
|
|
||
|
Jon Close |
Agree, except for the bit about 1/2.5" (0.4 inch diameter) sensor starting as 2.5" diameter disk. I don't think this is so. What I've read is that the silicon wafers used to make CCD and CMOS sensors are a standard 8" diameter disk. The sensors (regardless of size) are created on the surface of the 8" wafer and cut apart. 1/2.5" is most popular for digicams because it strikes a good balance between cost and performance for the point-n-shoot market. The smaller the sensor, the more that can be made from a single 8" silicon wafer with lower % of defectives. But the smaller the sensor, the greater the digital "noise" and the less sensitive it will be.
|
|
|
|
||
|
Alan N. Marcus |
Thanks Jon, I goofed on the size of the starting disk. Happy to have you around. Alan Marcus
|
|
|
|
||
|
John G. Clifford Jr |
Another reason the sensors are small is because it allows the camera to be small, the lens to be small, etc. The big benefit of the point-and-shoot digicams is that you can fit them in your pocket. Really, the image quality from these little cameras is amazing. Certainly way better than the average 110, 126, or disc film cameras that used to fill the niche.
|
|
|
|
||
|
This old forum is now archived. Use improved Forum here
Report this Thread |
||